Influence of nitrogen and potassium on Eucalyptus globulus Labill. mother plants

Abstract

In Portugal the traditional propagation of Eucalyptus globulus Labill (E. globulus) by seed is being replaced by vegetative propagation by stem cuttings. However, for E. globulus, there is no sufficient information related to the management of mother plant fertilization. So, it is important to study the relationship between the fertilization of the mother plant and the rooting ability of the cuttings.

With the aim of evaluating the effect of nitrogen and potassium on E. globulus mother plants, a fertilization experiment was performed during 2 years. 2 clones of E. globulus (clone HD161 and clone CN5) were fertilized, periodically, with 6 different nutrient solutions corresponding to 3 levels of nitrogen (50, 100 and 200 mg N L^-1) and 2 levels of potassium (50 and 100 mg K L^-1). In 1998, stock plants were subjected to formative pruning. In 1999, biomass, number of cuttings produced by the mother plants and rooting ability of the cuttings were evaluated.

With the two levels of potassium applied no significant effects were found.

On the contrary, increasing levels of nitrogen applied to the mother plants led to: i) an increase of total biomass, ii) a higher production of stem cuttings, iii) an improvement of the rooting ability of the cuttings.

Results showed that nitrogen fertilization and, as consequence, nitrogen reserves, constitute a limiting factor for rooting in E. globulus cuttings. Thus, research on the optimization of nitrogen fertilization of E. globulus mother plants should be performed.